A search and rescue dog works at the Oso mudslide site on March 29, 2014 in Oso, Washington.

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DARRINGTON, WA - Many of the dogs that have been essential in the search for victims of the deadly mudslide that buried the mountainside community of Oso will take a two-day break after long hours in the cold and rain, rescue crews said Sunday.

The dogs can lose their sensing ability if overworked, officials said.

"The conditions on the slide field are difficult, so this is just a time to take care of the dogs," said Kris Rietmann, a spokeswoman for the team working on the eastern portion of the slide, which hit March 22 about 55 miles northeast of Seattle and is one of the deadliest in U.S. history.

Dogs from the Federal Emergency Management Agency that arrived more recently will continue working, said Heidi Amrine, another spokeswoman for the operation.

Late Saturday, authorities revised the number of people believed to be missing from 90 to 30, while the official death toll increased by one, to 18, said Jason Biermann, program manager at the Snohomish County Department of Emergency Management.

Officials have said they had expected the number of missing to change as they worked to find people safe and cross-referenced a list that likely included partial information and duplicate reports.

Authorities have said they recovered more than two dozen bodies, but they won't be added to the official tally until a formal identification is made. Underscoring the difficulty of that task, Biermann said crews are not always discovering complete remains.

Crews have completed a makeshift road that will link one side of the debris field to the other, significantly aiding the recovery operation.

They have also been working to clear mud and debris from the highway, leaving piles of gooey muck, splintered wood and housing insulation on the sides of the road.

Searchers have had to contend with treacherous conditions, including septic tanks, gasoline and propane containers. When rescuers and dogs leave the site, they are hosed off by hazardous materials crews.

The slide dammed up the North Fork of the Stillaguamish River, causing water to pool up on the east side. The river cut a new channel through the mud, but the rain has raised the water level nearly a foot, Rietmann said.

In at least one place, the water level got so high that it covered areas that have already been searched, said Tim Pierce, leader of Washington Task Force 1, a search-and-rescue team.

"At this point, there's no point in searching (that area) again until the water drops back down," he said.

Rescuers should get some relief soon. Conditions were improving Sunday, and mainly dry weather is forecast Monday through Wednesday in western Washington.

The size of the debris field is also smaller than initially thought, officials said Sunday. After review and analysis, geologists have determined it is about 300 acres -- just under half the size of an earlier projection of 1 square mile.

Away from the whirring chain saws and roaring bulldozers, many residents of nearby Darrington sought comfort in church services.

"I can only compare it to a hot, hearty meal after a very cold day," said Slava Botamanenko, who works at the hospital in Arlington. He said he spent two nights there to be sure he was available for work after the mudslide blocked the road.

All week, a steady stream of people has stopped in to pray at the Glad Tidings Assembly of God on the edge of town, said Lee Hagen, the senior pastor.

"At a time like this, everybody knows they've got to have God's help," he said.

Country singer Susie McEntire, sister of Reba, performed for the congregation Sunday, crooning: "You'll get through this and you'll break new ground."

At the St. John Mary Vianney Catholic church a few blocks away, Father Tim Sauer said: "Bless our communities, bless our people, bless our valley."

The Rev. Owen Couch, a chaplain for the fire district in Darrington, said he's worried about the first responders.

"My concern is when this slows down and they're not going full tilt, and they have time to kind of reflect on what they've seen and what they've done," he said. "That's when the critical incident stress starts to kick in."

Steve Huot, lead chaplain for the Arlington Fire Department, said he is seeing people in various states. Some are in shock, while others have begun to grasp the reality of the disaster. Many are exhausted.

"It's more about listening right now. You need to encourage them and maybe change their focus to staying busy for the group, for the team," he said.

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